Update README.md (#231)

Author: hugohil

README.md

@@ -9,6 +9,10 @@ You can learn more about this project from this [talk at LibreGraphicsMeeting 20
 
 ## Getting started
 
+There is two different things at work here :
+- libprocessing (this repo) is the low-level cross-platform library for the core Processing API. It's written in Rust, and thus lets write Processing sketches in Rust.
+- mewnala is a Python package built directly from libprocessing, providing Python bindings for the library. It's available as any other Python package out there and lets you write Processing sketches in a Python environment, regardless of you having libprocessing or Rust installed.
+
 ### mewnala (the python library)
 
 Inside of our `processing_pyo3` crate we have created a python package that you can easily install with pip.
@@ -28,21 +32,65 @@ powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | ie
 ```
 
 #### Install a mewnala
+
+We're going to create a folder named `mewnala-sketchbook` and install the `mewnala` package inside:
+
 ```bash
 # Initialize a project with uv
 uv init mewnala-sketchbook && cd mewnala-sketchbook
 
 # add the package
 uv add mewnala
+```
+
+Now create a file named `sketch.py` at the root of `mewnala-sketchbook`.
+
+You can use this code to test
+
+```python
+from mewnala import *
 
+def setup():
+    size(400, 400)
+    background(255)
+
+def draw():
+    push_matrix()
+    translate(mouse_x, mouse_y)
+    fill(255, 100, 200)
+    circle(0, 0, 50)
+    pop_matrix()
+
+run()
+```
+
+Now run your sketch using:
+
+```bash
 # run a sketch
 uv run sketch.py
 ```
 
+_Note: you can use any file name you want for your sketch_
+
 ### Rust (libprocessing)
 
 You'll need to install the Rust toolchain to work on this project. Most users will want to install Rust via [`rustup`](https://rustup.rs/), which helps manage Rust toolchain versions.
 
+### Clone the project and its submodules
+
+When cloning this repo (or your fork), don't forget to install its submodules (eg. Lygia)
+
+```bash
+git clone --recurse-submodules git@github.com:processing/libprocessing.git
+```
+
+if you already cloned the repo without `--recurse-submodules`, you can run
+
+```bash
+git submodule update --init
+```
+
 ### Build commands
 
 This project uses [just](https://github.com/casey/just) as a command runner:
@@ -65,6 +113,12 @@ Install [wasm-pack](https://rustwasm.github.io/wasm-pack/):
 cargo install wasm-pack
 ```
 
+On Windows, you'll need to manually install `wasm-opt`
+
+```bash
+cargo install wasm-opt
+```
+
 You'll also need the wasm32 target:
 
 ```bash
@@ -84,6 +138,7 @@ This outputs the package to `target/wasm/`.
 ```bash
 just wasm-serve
 ```
+_Note: you'll need python installed on your machine to run this command_
 
 
 ## Contributing